In the prior art, the diversity receiving device for implementing an improvement of receiving quality by providing a plurality of receiving branches has been proposed (see Patent Literature 1, for example). The diversity receiving device disclosed in Patent Literature 1 at first chooses any one of two receiving branches and executes an error detection of information signal, and continues at the reception through this branch and turns OFF a power feed to the other receiving branch when no error is detected from the information signal (single receiving mode 1). Then, when the receiving environments are changed in the single receiving mode 1 because of transit, or the like and an error rate of the information signal exceeds a predetermined value, an effective range of the information signal is expanded by restarting a power feed to the other receiving branch and switching the receiving mode from the single receiving mode 1 to the diversity receiving mode.
In the diversity receiving mode, the received quality is detected by a square error of the information signal, the square error is compared with a predetermined threshold. Then, when the receiving environments are changed because of transit, or the like and the square error becomes smaller than the threshold, it is decided that the receiving environments are improved, and the receiving mode is shifted to the single receiving mode 1. Also, in the diversity receiving mode, an error detection of a control signal is carried out to measure an error rate of the control signal. Then, when the receiving environments are changed because of transit, or the like and the error rate exceeds a predetermined value, it is decided that the normal reception of the information signal cannot be carried on. Thus, the playback of the information signal is stopped and also the receiving mode is shifted from the diversity receiving mode to a single receiving mode 2.
In the single receiving mode 2, the diversity receiving device chooses any one of two receiving branches and makes an error detection of the control signal continuously. At this time, the diversity receiving device turns OFF a power feed to the other receiving branch. Then, in the single receiving mode 2, when the receiving environments are changed because of transit, or the like and the error rate of the control signal becomes smaller than a predetermined value, it is decided that the quality of the received signal is improved. Thus, a power feed to the other receiving branch is restarted and the receiving mode is shifted from the single receiving mode 2 to the diversity receiving mode.
Patent Literature 1: JP-A-2004-320528